With the development of the display technology, flexible display devices are applied more and more widely. The flexible display devices include different types, such as organic light-emitting diode display devices, electrophoretic display devices, liquid crystal display devices and the like. Apparently, a base for a display substrate of a flexible display device (e.g., an array substrate of a flexible organic light-emitting diode display device) must be a flexible base. The flexible base is mainly made of polyimide, polyethylene glycol terephthalate and other organic materials.
As the flexible base is easy to deform, it is difficult to position, transport and store the flexible base during the preparation process of a display substrate. For this reason, as shown in FIG. 1 and FIG. 2, usually, a flexible material layer 2 is formed on a glass base 1 at first, then a buffer layer 4 and a display structure 9 (including thin film transistors, a data line, a gate line, a capacitor, an anode, a cathode, an organic light-emitting layer, a pixel defining layer and so on, these components being not marked in the figures) are formed on the flexible material layer 2 in turn, and the flexible material layer 2 is irradiated from the glass base 1 side by ultraviolet laser, so that the adhesion between the flexible material layer 2 and the glass base 1 is reduced, and the flexible material layer 2 is thus separated from the glass base 1 (i.e., laser lift-off) so as to form an independent flexible display substrate (at this time, the flexible material layer 2 becomes the flexible base 21).
Meanwhile, a flexible array substrate includes a plurality of display units arranged in form of an array, and each of the display units usually includes a thin film transistor. Low-temperature polycrystalline silicon (LTPS) thin film transistors are one important type of thin film transistors, and the active regions 911 thereof are made of polycrystalline silicon. The manufacturing method of the active regions 911 is as follows: forming an amorphous silicon layer at first, then irradiating the amorphous silicon layer from one side away from the glass base 1 by ultraviolet laser (excimer laser), fusing, nucleating, growing and transforming the amorphous silicon into polycrystalline silicon by excimer laser annealing (ELA), and finally patterning the polycrystalline silicon layer to form the active regions 911.
The inventor(s) has found that at least the following problems exist in the prior art:
First, during laser lift-off, a part of laser may irradiate onto the display structure by passing through the flexible material layer, so that the performance of the display structure is influenced; for example, if the laser irradiates the active layers of the thin film transistors (particularly, metal oxide thin film transistors), threshold voltage drift and other adverse effects will be caused.
Second, for an array substrate having low-temperature polycrystalline silicon thin film transistors, during laser annealing, the laser may irradiate onto the flexible material layer by passing through the amorphous silicon layer, so that the performance of the flexible material layer is damaged, for example, the flexible material layer is carbonized or separated from an adjacent layer (e.g., a buffer layer).